Microwave directive antenna



Dec. 3, 1946.v c. B. HLFELDMAN ETAL 2,411,872

MICROWAVE DIRECTIVE ANTENNA v Filed June 11, 1942 ATTUNEY PIPE 20 v .highly directive end- Patented Dec. 3, 1946 UNITED, STATE s PATENT annahm GFI-*ICE MICROWAVE DIRECTIVE ANTENNA can n. 1r. Feidman, Mueller, 4 Bell Telephone Jackson Heights, Nr Y.,.

Laboratories, Incorporated, New

Rumson, N. J., and George E. -v

assignors to York, N. Y., a corporation of New' York Application June 11,1912, semi Np. 445,532

This invention relates to antennaarrays and V more particularly to microwave end-on antenna `arrays.

As is known,'in the microwave or centimetric" field open-ended metallic air-filled guides and horn antennas, and broadside arrays comprising simple pipe antenna units or horn units, have been suggested for emitting and collecting radio f energy. Also, leaky air-filled pipe antennas o f unit steerable array of the broadside MUSA type,

end-on unitsor subarrays are advantageous, -it now appears desirableto securev a highly efdcient 'end-on unit or a ysub-array of end-on unit antennas; A broadside antenna, an endon antenna and an oblique antenna are here denned' as antennas in which' the angles between the maximum direction of radio action and the anand therefore a given phase velocity at the operating frequency. and a'given length. Each of the remaining vguides has a b width and a phase velocity dependent upon its physical length, and

a phase length o r'over-all phase vangle'shiit de pendentupon its b width and physical length In tliegcase of transmission, theenergy o r wave- .let-emitted by each vof the remaining guides and propagated in the desired end-on direction, and thelwavelet emitted by the shortest guide and -having a similar propagation direction are in phase'agreement and combine to produce an additive eifect along the axis ofthe system. Consequently. the wavelets from all end-on pipe radiatorsl combine to produce an extremely sharp,

' nxed',1 end-on maximum lobe analogous to the comb antenna lobe 39 or illustrated in Fig. 5 of Patent `2,236,393, H. 'Il'. Friis and A. C. Beck,

` granted March 25. 1941. Conversely, when used tenna axis are substantially 90 degrees, 0 degreesy y and acute, respectively. It is one object 'of on antenna radio action.v

Itis another object of this invention to obtain` anend-on 'microwave array comprising a plurality of end-on elemental or unit antennas. i J

this invention to cuminl f small transverse guide ldimension a.

It is still another object of this invention to' y secure a small compact subarray ofend-on units.

suitable for use as a broadside MUSAv unit.

According to one embodiment of .the invention, a plurality as, for example, twenty, of air-filled -open-ended metallic rectangular wave guides or pipes are positioned parallel to each .other and aligned with the path of desired end-on radiation for receiving; the differently phased wavelets ab-A sorbed at the two above-mentioned pipe apertures and having the aforementioned errl-on direction have a cophasal relation at the .receiverI by reasonA of the difference in phase velocity and phase length ofthe two guides. While, as disclosed in the ll?roceedin gs of their. R. E., Decemand 1501, various types of ber 193 ,ipages 1500 guided ave components'may be used with rectangular pipe radiators orcollectors. the inven' j tion will be explainedin` connection with-the transverse electric component of the Haiiwave,

'which component is' polarized parallel to' th The invention wm be more muy understoodfrom a 'perusal of the following speciilcation taken in conjunctiony with the drawing on which like reference characters denote elements of sim- A or reception. As used herein the term "rectangular denotes a quadrangular figure other than square, and the term quadrangular includes -rectangular and square. The guides-have equal a or narrow transverse widths and graded physical lengths differing a given amount as, for example, one-half wave-length, so that vthe remote vopen ends or apertures are uniformly spaced in the direction of desired radio action. The extremities or terminals are connected directly to acommon dielectric channel and the associated translation device, which may be va transmitter or receiver, or to a scanning transceiver unit.

The shortest guide has a. given wide or b width,

ilar function and on which:

'Figs' L1, 2`and 3 are side, end andtopviews. respectively, of a simple embodiment of the j in vention; l

.-Figs. 4 and invention; and

Fiss. 6 and 'I are measured directive charac I teristics :of the embodiment illustrated by Figs.

v:ses y 4 and 5.

-Referring to Figsrl, 2 and 3,` reference nufmeral l designates a transceiver (TR) .which is I connected by/the main air-lled guide or dielectric channel 2 and coupling guide section Ito an end-on array 4 constructed in accordance with The l.transceiver device isof v'the the invention.

used infradlo scanning systype conventionally temsI and includes a pulse transmittencathodeare perspective and end views,A respectively, of ya 'preferred embodiment of they.

`ity vn and therefore the dimension bn of pipe n or pipe 5, hereinafter designated pipe o, and another rectangular air-filled metallic pipe 6, hereinafter designated pipe n, the far ends 1 of the pipes o and n being open-ended and constituting aperture-type elemental antennas and the near ends 8 being immediately adjacent to each other and directly coupled to the coupling section 3.

The longitudinal paths included in guides 2 and. 3 and extending between the device I and the.

near ends 8 are equal in electrical length. Pipes o and n are positioned parallel to each other and their longitudinal axes are aligned with the desired end-on direction or path 9' of radio action. Pipe o has a given wide transverse dimension bo and therefore at the operating frequency a given phase velocity vo. Also, it has a given physical length do and therefore a given phase time to=do/vo. Pipe n has a given physical length du greater by a predetermined amount KA than do, as explained more fully below, where x is the perating wave-length measured in free space and K is constant. Also, pipe n has a wide transverse dimension bn which, as also explained below, may or may not differ from bo. The narrow transverse l a dimensions of the pipes o and n are equal.

Since, as stated above and as shown by arrow I0,

the transverse electric component utilized is par-.

allel to the short pipe wall or side, the dimension a is the electric plane dimension. dimension b being the transverse magnetic plane dimension.

` In operation, assuming the array 4 is used for transmitting, energy is supplied by device I to the connecting waveguide 2 and through coupling wave guide 3 to the input or near-end terminals 8 of pipe o and pipe n. The wavlets entering pipes o and n have the same polarity and phase angle since the paths connecting the input aper-r tures to device I are'equal in length. yAs radiated,

the wavelets differ in phase angle an amount corresponding to the physical separation between the apertures 1 and dependent upon theb dimension of pipe n. More accurately, the phase angle of the wavelet emitted by aperture 'l of tube n is retarded relative to that emanating from aperture 'l of tube o by an amount t corresponding to the time interval in which the wavelet from pipe o travels in the ether medium alng path 9 to a 'point opposite aperture Tof pipe n, whereby the wavelets are propagated in direction 9 in phase agreement and in other directions in phase disy agreemena'and maximum radiation occurs end- Tvhe terms phase agreement and coon. phasal, as used herein signify that the energies have the same phaseA angle values and similar instantaneous polarities or have angles diiering by 360 degrees or a multiple thereof and similar po larities. Conversely, when used for the'collection of energy, the wavelets incoming -in a direction opposite to directionl 9 have at any given instance a phase angle difference related-to the spacing K)\,1and by reason of'the phase velocity characteristics and phase lengths of pipes o and n these wavelets have, upon arrival at the transceiver l,

a cophasal relation whereby maximum .reception c" occurs end-on. As explained below in connection with Figs: 4 and 5, additional pipe radiators may be employed to enhance the end-on action.

lConsidering the operation ofy the array 4 from a mathematical standpoint, 'if bo, do, vo,to and d plane i I, which is perpendicular to direction 9, in

phase agreement at plane Il. Conversely, the

out-of-phase energies absorbed at apertures l.

from a wave having its front in plane I I arrive in phase agreement at device I. The method of as= certaining the values for the phase velocity an, the width bn and the phase time tn (=d/n/v) of pipe n will now be explained.

A careful.distinctionshould be made between vo, the velocity of phase propagation or the phase velocity, which is an apparent rather than an actual velocity, andthe actual velocity of energy propagation of the wave Within the air-lied guide. As explained in the two articles Rectangular hollow pipe radiators by W. L. Barrow and F, M. Greene and Waves in hollow tubes of rectangular cross section by L. J. Chu and W. L. Barrow, both published in the Proceedings of the I. R. E., December 1938, the phase velocity in an air-filled rectangular guide and the propagation velocity depend upon'the ratio of the operating frequency to the guide cut-01T frequency, the width b and the dielectric constant of the material constituting the channel. See especially pages 1532 and 1540, I. R. E. Proceedings, December 1938, and seealso Patent 2,106,768, G. C. Southworth, February 1, 1938; Wireless Engineering," March 1942, page 93 and two articles Hyper-frequency wave guidesmathematical theory vby IS. A. Scheikunoiet al., and Hyper- 'frequency Wave guides-general considerations" by G. C. Southworth, both published in the Bell System Technical Journal, April 1936. As the b width approaches the cut-oil? dimension, the op.. erating frequency being constant, the propagation velocity becomes' a fraction of the free space propagation velocity while the phase velocity becomes a multiple of the free space propagation velocity. In an air-filled guide the phase velocity is always greater than the free space velocity.'

Hence, while the two guides may have the same physical length, their phase lengths may be dii'- ferent, depending upon the relation of their b dimensions and the phase velocities.

In order to secure phase agreement between the wavelets emitted at the apertures I ofthe two pipes o and n, the spacing K). between apertures being a constant, the phase time tn of pipe n. must have the value given by the followingequation where dn=the given physical length of pipe n c=the free space velocity I A7\=the operating wave-length as measured in air l' Equation 2 equates the phase time for pipe n For the two-element system with the phase time for pipe o -to which has been added the phase time of the spacing. The `phase time for pipe n, in terms of its own velocity is:

tnrdo-i-vnK).

tn as given by Equation 3 we get Multiplying both sides of Equation 5 by c we have l y (a) and by substituting in vEquation 2 the value of From thehteaching lon page 1532, Proceedings Referring now to Figs. 4 and,5, the array 40,

The near end apertures 42 of pipes 4I are adjacent each other and directly connected to the coupling section 3.l The twenty-one pipes are aligned with the desired direction 9 of radio action and have uniformly graded lengths do, di, da dao, as shown in Fig. 4, so that the spacing between thefar end apertures 43 of -each pair of adjacent pipes isKA, and the spacing between the aperture 43 of pipe o and aperture l43 of any other pipe is nKA, wheren corresponds to the pipe designation. The a or electric plane widths are the same for all pipes.

bzoor magnetic plane widths vary as shown in the enlarged end-view, Fig. 5, since the b Widths of pipes 0, I, 2 20 are critically dimensioned as explained above in connection with Figs. 1, 2 and 3. The b width variations are-not The bo, b1,

shown in Fig. 4 inasmuch as the scalel employed does notpermit detail illustration of these widths. The operation' of the system of Figs.. 4 and 5 is believed to be apparent in view ofI the explanation given above relative to the two-element system. In the case of transmission, the radiations from the twenty pipes'add in phasev for direction 9 and in the case oi.' receiving maximum reception occurs in a direction opposite to that represented by arrow 9. In a system actually constructed in accordance with Figs. 4 and 5 highly efcient end- A on action was obtained. The dimensions of the system actually constructed are given in .the table l below.

Pipe Pipe b Pila-)N- v length 'L2 iN. width in d in A c cm.

do 1 2 0 bo 5. 6580 di 1.5 3/2 0 v bi 0. 5740 da 2. 0 4 -1 b2 5. 0006 da 2. 5 5/2 -1 b s. 3463 d4 3. 0 2 -1 b4 5- 6580 d5 3. 5 7/4 -1 bs 5. 9708 ds .4. 0 8/5 -1 be 6. 2770 d? 4. 5 3/2 ,-1 b1 5740 du 5. 0 2 -2 bl 5. 0580 du 5. 5 -2 be 5. 8463 d10 6. 0 12/7 -2 bm 0. 0328 du 6. 5 /8 -2 bil 6. 2155 du. 7.0 14/9 -2 b G. 3970 dia 7. 5 3/2 -2 bis 6. 5740 du 8. 0 16/9 -3 bu 5. 9265 dia 8. 5 17/10 -3 bis 6. 0592 die 9.0 18/11 -3 bie 6. 1904 d11 9. 5 19/12 -3 bi1 6. 3200 dis 10. 0 20/13 -3 013 6. 4479 du 10. 5 3/2 -3 bis 6. 5740 d20 11 22/13 4 bzo 6.0738

In the system tested y K was chosen tp be .1/2;`

do was chosen to be one wave-length, that is, X, and the velocity 11o in pipe o was chosen to`be 2c. Substituting these values in (7) gives 1L agli@ c'l n frei@ -If the arbitrary constant N were not utilized and if 'n were regarded zero we would have for pipe n- 10 a value of vin the above table. As shown bythese curves,

the maximum electric plane lobe 44and the maximum magnetic plane vlobe 451are aligned substantially with the axis 46 and the desired direc- A tion 9, the angle zero degrees being coincident with axis 46. More accurately, vin the magnetic plane, the principal axis 4of lobe 45 is exactly aligned with the zero'degree direction but in the electric plane the largest axis of lobe 44 is at a slight angle to the zero degree direction the slight deviation resulting, it is believed, from the coupling between the apertures 43.

mum lobe in both planes has a relatively narrow width and negligible secondary lobes 41.

Although'the invention hasbeen explained-in connection with speciiic embodiments, it is-not to be limited to the structures illustratedegsince other apparatus may be utilized in succe'ssfully practicing the invention. pipes of square or circular cross section or 'dielectrically loaded-pipes may be used in place of the`rectangu1arair-filled pipes. Also, any practical number of pipes may vbe used and, instead Also, as shown by the` curves of Figs. 6 and 7, the maxi- 7 of uniformly graded pipe lengths do, di, d2 d20, the physical lengths of the pipes may obviously be non-uniformly graded, provided that the phase velocities of the pipe are properly proportioned in accordance with the lengths.

What is claimed is: 1. An end-on antenna array comprising a plurality of open-ended dielectric channels having different phase velocity characteristics.

2. An antenna array comprising a plurality of .open-ended dielectric channels having different lengths.

3. An end-on antenna array compri-sing a plurality of open-ended dielectric channels having different cross-sectional areas.

4. An antenna array comprising a pair of parallel dielectric end-on antenna members having different physical lengths and different phase velocity characteristics, the velocity 'diierence being a function of the length diierence.

5. In combination, a pair of parallel end-nre dielectric radiators having different lengths and different widths, the difference in width being a function of the length diierence.

6. An antenna array compri-sing a plurality of parallel rectangular open-ended wave guides having different wide transverse dimensions, the open ends of said guides being spaced on the desired wave path an amount dependent upon the difference in said dimensions.

11.v In combination, a radio transceiver, a plurality of air-filled parallel rectangular metallic Wave guides connected thereto and having apertures at their remote ends, said guides having different physical lengths and diil'erent wide transverse dimensions, the wide transverse dimension of the longer guide being a function of the physical length of said guide and the phase length of the shorter guide.

12. In combination, a radio translation device. a'first open-ended, metallic wave guide connected thereto and having a given phase velocity and a given phase length differing from its physical length, a second open-ended metallic wave guide connected to said device and having a greater `physical length, said guides being parallel and aligned With a desired direction of action, said second guide having a phase velocity diiering of one 'guide being equal to the phase length of the other guide plus said length diierence.

8. A dielectric antenna array comprising a pair of dielectric channels connected to a translation device and having apertures at their` remote ends, said apertures being spaced on the path of desired radio action, said channels having for a given frequency different phase velocities, the phase velocity difference being a function of ,the aperture-spacing.

9. An end-on dielectric antenna array comprising apair of open-ended parallel -dielectric channels having different lengths and connected to a translation device, said channels having different physical lengths and phase velocities differing by an amount related to the physical length difference and such -that the difference in -phase length of said channels equals the difference in physical length or equals the last-mentioned difference plus or minus a multiple, including one,

of ajwave-length as measured in the ether.

10. An antenna array comprising a plurality of open-ended, air-filled, metallic rectangular Wave guides having a given' difference in physical length as measured in Wave-lengths in the ether medium and aidiierence in phase length as measured in wave-lengths in the guides, said guides having a 4difference in their wide transverse dimensions from that of the rst guide by an amount such that the difference in phase length of said guides is equal to the difference between the physical length of said guides.

13. A dielectric antenna array comprising a pair of parallel open-ended metallic wave guides aligned substantially with a desired direction of action and having diierent physical lengthsfsaid guides having a difference in phase velocities proportioned to secure a difference in phase lengths equal to the diierence in their physical lengths.

14. In combination, a translation device, a plurality of dielectric channels connectedthereto and having antenna apertures spaced on the path of desired radio action substantially, the adjacent channels having at least one dimensional difference related to the spacing between the associated apertures whereby the relative phase velocities in said adjacent channels are such that the wave-lengths as received at said device from a Wave traveling on said path are cophasal and the wavelets emitted along said path are cophasal and form a wave front perpendicular to said direction. I

15. An end-on dielectric antenna array comprising a plurality of end-on dielectric' antenna.

members, each member comprising an air-filled open-,ended rectangular metallic wave guide having a narrow transverse dimension and a wide transverse dimension and connected to a transceiver for utilizing waves polarized parallelto the .narrow transverse dimension, said members having graded lengths and graded transverse wide dimensions, the transverse Wide dimension of any intermediate member being a function of the sum of the length of the shortest member and the difference in length between said intermediate member and said shortest member.

CARL B. H. FELDMAN., GEORGE' E. MUELLER. 

